Photoacoustic detection of trace gases with an optical microphone

An alternative to the electrical microphone for photoacoustic detection of trace gases is presented. This new microphone is made of standard monomode optical fibers wound and glued on a thin plate and is one of the arms of a Michelson interferometer. A detection scheme with a Sagnac interferometer has also been used and has given better results. Three cells working with different resonance modes and different microphone configurations have been tested.